This invention is directed to a cold cathode, grid-controlled, crossed-field switch which can be repetitively operated in the presence of a fixed magnetic field.
Although this cold cathode discharge device has utility as an amplifier, in the context described herein, the device has primary utility as a closing switch in high frequency pulsed electric power distribution systems or networks.
Background patents of general interest describing the developments in crossed-field switches include U.S. Pat. Nos. 3,638,061; 3,641,384; 3,604,977; 3,558,960; 3,678,289; 3,769,537; and 3,749,978.
In this group, U.S. Pat. No. 3,638,061 permits conduction for reasonable lengths of time without off-switching due to gas losses.
U.S. Pat. No. 3,641,384 describes a unique electrode arrangement in which the electrodes are serially connected to achieve higher holdoff voltages during nonconduction.
U.S. Pat. No. 3,604,977, in a two-electrode crossed-field switch, uses a fixed magnetic field having a field strength above the critical value to enable conduction. One of the electrodes is used to produce a bucking field to reduce the field strength below the critical value for offswitching.
U.S. Pat. No. 3,558,960 introduces an arrangement for maintaining gas pressure in a crossed-field switch for controlling conduction.
U.S. Pat. No. 3,678,289 describes an arrangement for off-switching a crossed-field switch by temporarily reducing the magnetic field to a field strength at which the switch becomes nonconductive.
U.S. Pat. No. 3,769,537 describes a two-electrode crossed-field switch having one perforated electrode and having a baffle adjacent some perforations in a position to limit the maximum electron path length in the absence of a magnetic field to minimize or obviate a reduction in the holdoff voltage.
U.S. Pat. No. 3,749,978 describes the use of sequentially discharged capacitors coupled to an offswitching pulse coil to maintain the magnetic field below the critical value for a desired period.
U.S. Pat. No. RE. 27,557 describes a network of sequentially switched crossed-field switches for increasing circuit resistance.
These patents are of general background interest in setting forth the environment in which crossed-field switches operate, in describing structural details and parameters, and in describing unique switching controls in two-electrode crossed-field switches.
U.S. Pat. No. 4,034,260 is of greater interest in that it describes a three-electrode crossed-field switch. Here, a control electrode, which can be called a grid, is pulsed to electronically switch the tube to a conducting condition. The presence of a magnetic field is required in both the grid-cathode gap and the anode-grid gap for proper triggering and conduction. Off switching is achieved by suppressing or switching off the magnetic field. In this arrangement, the magnetic field may not be fixed but must be cycled for repetitive on and off-switching operation.
Analogies may be drawn to conventional vacuum tubes or the thyratron. But, these are examples of switching devices having thermionic cathodes rather than cold cathodes. Thermionic cathodes have heat sensitive coatings to release electrons in the presence of heat. Thus, a heater is required to boil off the electrons.